1. Technical Field of the Invention
This invention relates generally to wireless communication systems and more particularly to multiple frequency band wireless communications.
2. Description of Related Art
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, et cetera communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of the plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via the public switch telephone network, via the Internet, and/or via some other wide area network.
For each wireless communication device to participate in wireless communications, it includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier. The data modulation stage converts raw data into baseband signals in accordance with a particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier amplifies the RF signals prior to transmission via an antenna.
As is also known, the receiver is coupled to the antenna and includes a low noise amplifier, one or more intermediate frequency stages, a filtering stage, and a data recovery stage. The low noise amplifier receives inbound RF signals via the antenna and amplifies then. The one or more intermediate frequency stages mix the amplified RF signals with one or more local oscillations to convert the amplified RF signal into baseband signals or intermediate frequency (IF) signals. The filtering stage filters the baseband signals or the IF signals to attenuate unwanted out of band signals to produce filtered signals. The data recovery stage recovers raw data from the filtered signals in accordance with the particular wireless communication standard.
For a wireless transceiver to operate in accordance with a particular wireless communication protocol, it must be designed to receive and transmit radio frequency (RF) signals within a given carrier frequency band using a particular baseband encoding, modulation, and/or scrambling protocol. For instance, IEEE 802.11 a prescribes a frequency bands of 5.15-5.25 GHz, 5.25-5.35 GHz, and 5.725-5.825 GHz, using a modulation scheme of binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), sixteen quadrature amplitude modulation (16-QAM), or sixty-four quadrature amplitude modulation (64-QAM) and convolutional coding having a coding rate of ½, ⅔, or ¾. As another example, IEEE 802.11b prescribes a frequency band of 2.400 to 2.483 GHz and modulates that wave using Direct Sequence Spread Spectrum (DSSS) or Frequency Hopping Spread Spectrum (FHSS). As yet another example, IEEE 802.11g prescribes a frequency band of 2.400 to 2.483 GHz using a modulation scheme of binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), sixteen quadrature amplitude modulation (16-QAM), or sixty-four quadrature amplitude modulation (64-QAM).
From the above examples, for a wireless transceiver to operate in accordance with IEEE 802.11a, it must be able to transmit and receive RF signals in one of the 5 GHz frequency bands, while, to operate in accordance with IEEE 802.11b, or g, the wireless transceiver must be able to transmit and receive RF signals in the 2.4 GHz frequency band. Because of the substantial difference in frequencies and the design of the transceiver, a wireless transceiver cannot effectively transmit RF signals in the different 5 GHz frequency bands and/or in the 2.4 GHz frequency band. Nevertheless, attempts have been made to integrated multiple frequency band transceivers as described in “A Single-Chip Digitally Calibrated 5.15-5.825 GHz 0.18 μm CMOS Transceiver for 802.11a Wireless LAN”, By Jason Vassiliou et, al. IEEE Journal of Solid-State circuits, Volume 38, No. 12, December 2003; and “A Single-Chip Dual-Band Tri-Mode CMOS Transceiver for IEEE 802.11a/b/g WLAN”, by Masoud Zargari, et. al., ISSCC 2004/Session 5/WLAN Transceivers/5.4.
While the prior art is making advances in wireless transceivers, there exists a need for an integrated multiple band direct conversion wireless communication transceiver.